Are we selectively breeding for predisposition to laminitis?

Let’s take a break from scientific, evidence-based information and play around with speculation. This article is a collection of speculation from myself and other people with scientific backgrounds regarding possible reasons why we might be inadvertently selectively breeding horses that are predisposed to Insulin Dysregulation and laminitis. I will not include the names of the speculator to protect their scientific credibility.

There was a time when I was attending conferences focused on laminitis or equine metabolic disease several times per year. Chatting in the hallways between lectures and around the luncheon table, and the Q & A session after lectures were often the best part of the conference for me. It’s where scientists say things speculatively, off the record, without peer review. Good speculation can sometimes evolve into a theory worthy of further investigation or may bomb out when someone else provides evidence to the contrary. It’s an entertaining thought exercise for curious minds. Feel free to disagree. My opinion and $5 will buy a cup of coffee.

Q: Why do Mustang’s tend to be Insulin Dysregulated?

There is an area of the Atlantic Ocean called ‘The Horse Latitudes’. This section of the ocean got its name because it often lacked wind and rain. When sailing ships of early explorers heading for the Americas were becalmed, dead horses were thrown overboard when they ran out of food and water. It would have made good sense to choose obese horses for transport, as they were more likely to survive the voyage. This created a genetic bottle-neck such that the horses imported by Spanish explorers that were the basis of the American Mustang were comprised of stock tending to be ID.

The Daisy Cutter Hunter

When the study describing a genetic predisposition to laminitis in an inbred herd of Welsh ponies was presented, (1) it created quite a stir at a conference where I also presented. No one ever mentioned the lineage or the farm where the study was done and it was understood that is was not to be public knowledge. I admit to being nosy, and I just love detective work. I put together a few rumors with the well-known people present at the conference, made note of some vague descriptions of the farm from the study paper, did some Googling, and I figured out which line of ponies was involved. They are highly sought after as children’s hunters, and win consistently, having the desired gaits for show hunters.

I happen to know a pony from the same lineage, as a friend was training him. He had laminitis in the past from the wrong kind of hay but recovered well with more careful attention to his diet. I was boarding my mares at the same facility while I went to another conference. I needed to talk to my friend before leaving, so I watched her school this Welsh pony while I waited. When he did extended trot across the dressage ring, I noticed him moving sort of stiff-legged and flipping his toes up and thought ‘if my mares moved like that I would be concerned’. My excellent farriers had taught me that toe flipping is a sign of subtle, sub-clinical laminitis so I had developed a keen eye for it. I watched it come and go with my own mares. When a horse has slightly sore toes but is not obviously lame, they change the way they move and put their feet down. They move their legs more from the shoulder, keeping their knees straighter than normal. Just before the foot lands, they flip their toes up with an exaggerated heel-first landing to limit concussion on their sore toes.

So I go to this new conference, and another facet of the same pony study was presented. The researcher who did the statistics on the study loved playing with numbers. When the farm where the pony study was done had a dispersal sale, this researcher collected sale prices on the ponies and ran correlations with the numbers from the blood work. She was very surprised to find that the ponies that had genetic and hormonal predispositions to laminitis sold for a higher price! She said ‘it appears that there may be some desirable characteristic creating selection pressure for predisposition to laminitis’. Being a good scientist in public, she didn’t speculate as to what that might be. I had an epiphany! When her Q & A started, my hand was stabbing the air. She didn’t have time for my question, so I pounced on her as she left the room. “I know what it is! It’s the daisy cutter action”. She said, “Yes, I think so”. The most desirable way of going for a hunter is very similar to the way a horse goes with slightly sore toes.

Q: Why are gaited breeds predisposed to laminitis?

Let’s continue with speculation. Breeds that amble or ‘gait’ are commonly noted to be at high risk for laminitis. Breeds that gait or amble mentioned in scientific literature as being predisposed to Equine Metabolic Syndrome include: Paso Finos, Morgans (some are gaited), Tennessee Walkers, Saddlebreds, Marchador,Icelandic horses, and Rocky Mountain Horses. Both the tendency to amble and predisposition for laminitis are heritable traits. Gaited horses all have some form of a ground covering 4 beat gait, be it amble, foxtrot, running walk, paso, singlefoot, or rack. They are known to be comfortable for people with bad backs, fair maidens in days of old riding palfreys on rough roads, and people who need to stay in the saddle all day. In a four-beat lateral gait, each foot contacts the ground independently, in a smooth regular way that distributes the impact with the ground over all four feet. We benefit from this diminished impact, but perhaps a horse with slightly sore feet is also more comfortable in a four beat gait. Is it possible that by selecting horses with low impact, four beat gaits we that have inadvertently selected for horses with a tendency for sore feet?

A 40 year Tennessee Walker breeder came to one of my full-day clinics.
I asked her what percentage of TWH are predisposed to laminitis? She said, “All of them” .

“Big Lick” Tennessee Walking horses are those shown in competition performing an extreme version (perversion?) of the running walk. I’m already in enough trouble to link to videos, but if you want to see it, go to YouTube and search ‘Big Lick Tennessee Walking horse’. While I’ve been envious of some gaited horse riders that joined me for long rides in the mountains, the whole ‘big lick’ show scene just makes me sick.

Let this sink in: making TWH horses front feet sore gives them an unfair advantage in the show ring. It helps them win.

From: https://www.avma.org/sites/default/files/resources/Soring-Bookiet-March-2014.pdf

Physical methods are aimed to create pain when the horse’s hoof strikes the ground. This causes the horse to lift its legs faster and higher. Methods of physical soring include grinding or trimming of the hoof and/or sole to expose sensitive tissues or removal of the normal support structures of the hoof wall; inserting hard objects between the pads and the sole to place pressure on this sensitive area of the hoof; over-tightening of metal hoof bands to cause excessive pressure; improper shoeing techniques that violate the Horse Protection Act (HPA); and purposefully causing laminitis (founder), which is an extremely painful condition of the hoof.

Soring causes a horse to bring its hind limbs under itself as far as possible to reduce weight on the forelimbs. In the show ring, this might pass as a short cut to collection and to allow more extravagant action with the front legs. When gaited horses subjected to soring may adopt a stance known those circles as ‘bucket stance’ as they look like they are standing in a bucket. In ponies, it is known as ‘laminitis stance’.

Bucket stance in a Tennessee Walking Horse

Even the standard for flat shod TWH includes a lower hoof angle and longer toe than other breeds. Collapsed heels and feet that run forward are common on horses with chronic, sub-clinical laminitis. Which came first? The different standard or the acceptance that TWH feet often look like they have laminitis?

Might naturally occurring, sub-clinical, chronic laminitis create the same desirable gait? Is it just coincidence that Tennessee Walkers are known to have a predisposition to laminitis, or does subtle lameness lead to their selection as desirable breeding stock? It would not be the first time that selective breeding for a desirable characteristic overlooked its adverse effect on horse health. (search ‘Impressive Quarter Horse HYPP’, or ‘Overo Lethal White Syndrome’) Of course not all gaited horse owners are cruel, or pervert the natural gaits of their horses with shoes that essentially cripple them and prevent safe riding outside of a groomed arena. But as long as breed association shows give prizes to horses with underlying health issues and unsoundness, the health of that whole breed is jeopardized. Winners breed more. Those that love and care properly for their horses should accept that that for whatever reason, gaited horses are at higher risk for developing endocrinopathic laminitis. Owners should feed them accordingly and be vigilant for signs of laminitis .

Is fat beautiful?

As a former art student, when I travel I like going to art galleries. I particularly like Renaissance and Baroque artists from the realism period when artists focused on depicting reality instead of stylized interpretations. Maybe I’m not the only women who secretly wished I lived in a time when curvy women with ‘love handles’ and cellulite where considered beautiful, but then I don’t have hooves which are uniquely adverse to the effects of insulin.

Evidently, the horses of that time period were judged by the same standards of beauty. Cresty necks and lumpy apple butts that we now consider to be abnormal fat deposits associated with Insulin Dysregulation are common in depictions of horses from many hundreds of years ago. Occasionally upon close scrutiny, I have even seen collapsed heels and rings in the feet. ID in horses is not new. Apparently, we have found it to be beautiful for a long time.

We have been selecting horses for breeding and directing their evolution for at least 6,000 years. In our ignorance of the consequences, we may have allowed our own comforts and standards of beauty to direct that evolution to their detriment. Laminitis is the second leading cause of death in horses.

Now that we know better, which of the leaders in the horse industry are willing to redirect breeding and showing towards health and soundness?

(1)Evaluation of genetic and metabolic predispositions and nutritional risk factors for pasture-associated laminitis in ponies K H. Treiber, ; D S. Kronfeld, T M. Hess; B M. Byrd, R K. Splan, W. B Staniar, J of the Am Vet Med Assocn May 15, 2006, Vol. 228, No. 10, Pages 1538-1545

https://avmajournals.avma.org/doi/abs/10.2460/javma.228.10.1538

Katy WattsJune 22, 2020